To function most efficiently, muzzle loading firearms preferably have a projectile and a wad or gas check member between the projectile and the powder charge. In the early years of muzzleloaders, a lead projectile was ram-rodded down the bore of the firearm for placement over a powder charge. The diameter of the projectile, of necessity, exceeded the diameter of the bore for holding the projectile in place within the bore.
Later in the history of muzzleloaders came ordnance in which the wad was directly attached to the ball or bullet as typified by U.S. Pat. No. 35,273, issued to E. D. Williams and U.S. Pat. No. 43,017 issued to G. P. Ganster.
Since the early inventions, it has become common to use sabots or wrappers, surrounding the bullet, to engage the bore of the firearm to hold the projectile in place and, where the bore is rifled, to impart spin to the bullet. Such wrappers are conventionally made of expansive packing such a molding paper, leather or the like, as typified by U.S. Pat. No. 34,950, issued to C. T. James and U.S. Pat. No. 405,690, issued to A. Ball.
More recently it has been accepted practice to attach a discarding gas check directly to the base of the projectile. The gas check is typically made of resilient plastic material and has a diameter slightly greater than the minimum accepted barrel bore size. The attached projectile has a diameter less than minimum bore size, providing for a loose fit in the barrel bore. U.S. Pat. Nos. 5,458,064 and 5,621,187 are typical in this regard, and include a single recess in the rear of the gas check into which the powder charge often enters.
Primary disadvantages of known projectiles for muzzleloaders relate to dimensions of the bullet, placement of the gas check member, and the inability to keep the powder charge out of the gas check in a controlled manner.
Where the bullet's maximum diameter exceeds that of the bore of the firearm, scoring of the bullet from its contact with the rifling as well as deformation of the bullet from the rod-ramming process results, causing degeneration of the ballistic qualities of the bullet. Additionally, because of the contact between bore and bullet, the firearm is more difficult to load, thereby impeding the loading process when a follow-up shot may be needed in a hurry. Yet, some degree of engraving is desirable to improve ballistic performance.
Where wrappers or sabots are used to surround the bullet, such wrapper itself engages both bullet and bore and is indeed required where rifling of the bore is intended to impart spin to the wrapper and hence the bullet. Such wrapping, however, in surrounding the bullet and hence being located between bullet and bore, results in interference between the bullet and the bore, adversely affecting the ballistic qualities of the bullet exiting the bore. It also prevents the bullet from being properly engraved with the firearm rifling pattern.
Projectile diameters of less than bore size result in accuracy issues and possible hazard and extremely dangerous situations to shooters and bystanders.
Projectiles exiting bore without being engraved with the rifling and any projectile which is discarding gas checks, sabot or wrappers in flight are susceptible to inaccuracy in flight and inconsistent downrange ballistic performance.
It is therefore desirable to provide a projectile with at least part of its diameter greater than the bore of the firearm into which it is inserted, which can thereby gain the benefit of being engraved with the rifling of the bore through which it will be discharged while nevertheless avoiding the difficulties encountered with such greater-diameter bullets known in the prior art.
It is also desirable to provide a controlled air space to enhance propellant burn, to ensure integrity of this controlled air space to avoid its deformation during loading and firing, and to yield a consistent ballistic result from one firing to the next.
It is also desirable to have a pressure shield attachable to the bullet to ensure positive placement of projectile relative to the propellant and to ensure consistent pressures and increased velocities, while avoiding undesired entry of powder into the gas check.
It is also desirable to improve stability and uniform bullet flight without the adverse effect of a sabot, wrapper, or gas check being discarded.
It is also desirable to provide a projectile which is user friendly, which may be loaded and discharged with quick response time, and which is convenient to carry and handle.
It is further desirable to provide a means for expanding the projectile on impact, for increasing the length of the projectile to improve ballistic performance without a substantial increase in weight, for managing projectile weight, and for easily engraving the projectile with the bore rifling.